1. Field of the Invention
This invention relates to a camera which is equipped with an apparatus for detecting camera shake and, more particularly, to a camera having both the above-mentioned shake-detecting apparatus and an electronic viewfinder which forms an image of the photo subject on an area sensor and displays the image based on the output from the sensor. It also relates to a camera containing the above-mentioned shake-detecting apparatus and a focus-detection apparatus.
2. Description of the Related Art
Cameras with an electronic finder have been previously published. For example, such a camera is disclosed in a Laid-Open Patent Application Sho 62-35329. However, this camera does not contain an apparatus which detects camera shake.
On the other hand, cameras with an electronic finder which can also detect camera shake have also been published. One example is found in a Laid-Open Patent Application Sho 63-129328. According to the application, the shake-detecting camera with an electronic finder contains a CCD area sensor for detection of camera shake, and detects camera shake by comparing the image at one instant with that at another instant. However, this camera does not use the TTL method.
Furthermore, video cameras containing a shake-correcting optical system and an electronic finder have been published. One example is disclosed in Laid-Open Patent Application Sho 61-150581. In video cameras, the area sensor is used for picture-taking, and the electronic finder is used to follow the subject. In the case of conventional video cameras with a shake-correcting optical system, as in the one in the above application, camera shake is detected and corrected through an angular velocity sensor.
One problem arising in connection with the above-given conventional cameras is that the camera tends to become larger because it is equipped not only with an optical system and an area sensor for camera shake detection, but also with an electronic viewfinder which also comprises an optical system and an area sensor.
The camera in a Laid-Open Patent Application Sho 63-12932 described above does not include a shake-correcting optical system, and does not use the TTL method; therefore, it is not able to confirm the desired image's correction region. In the case of a video camera with a shake-correcting optical system and an electronic finder, although the shake-corrected image is viewable in the finder, the camera shake in the part of the camera where the image of the subject is formed cannot be corrected; consequently, the photo taken is blurred.
Moreover, because conventional cameras with an electronic finder and a shake-detecting apparatus do not use the TTL method, a parallax effect results. As a result, it has been difficult to correct the shake. Further, since video cameras which use the TTL method are not still cameras, it has not been necessary to consider the optical path.
On the other hand, while conventional auto-focus cameras contain a finder screen with a diffusing surface because the focal point is confirmed on this screen, conventional shake-detecting cameras perform the same function using a beam of light passing through the finder screen.
Where the finder screen has a diffusing surface, as in the case of conventional cameras, one problem has been that the beam which should strike the shake-detecting sensor becomes diffused and the light intensity on the sensor surface decreases. Another problem has been that the roughness of the diffusing surface creates an image on the sensor, which reduces the precision of the shake-detecting capability. On the other hand, if the finder screen were made transparent, there would be a different problem: though the light intensity on the shake-detecting sensor would increase, it would no longer be possible to confirm the focal point on the finder screen.
In addition, in order to perform detection and correction of image shaking using the photo-image detecting method, it is necessary to have a separate optical path for detection as well as a separate optical path for auto-focusing, since these operations are both performed during exposure.
One embodiment in which these two purposes are partly served by one optical path is published in a Laid-Open Patent Application Sho 57-133414. In this application, the optical path for auto-focusing is located Just under the pentaprism, and images for shake detection purposes are produced through a half-mirror.
As explained above, in order to perform detection and correction of camera shake using the photo-image detecting method, it is necessary to have a separate optical path for shake detection in addition to the optical path for auto-focusing. Consequently, because of the necessity of having two different optical paths, compact cameras with these capabilities cannot be produced.
Further, in the case of the embodiment where the two purposes are partly served by one optical path, not much beam is available, since the area that the half mirror can reflect is only a fraction of the finder's field of vision; subsequently, there has been a problem of insufficient light.